Today, there exist various examples of gerotors used as hydraulic pumps and motors. These gerotors comprises pressure chambers defined by interacting lobes of an inner rotor and an outer rotor. Gerotors are well known fluid directing units and typically comprise a hollow outer rotor provided with internal lobes and an inner rotor provided with external lobes.
Today, there exist two types of gerotors, which are Low Speed High Torque (LSHT) gerotors and High Speed Low Torque (HSLT) gerotors.
For the LSHT gerotors, the outer rotor is stationary and the inner rotor is located within the outer ring. The inner rotor has one less lobe than the outer rotor and has an axis of rotation which is offset or eccentric relative to an axis of the outer ring. The inner rotor is eccentrically disposed within the outer rotor. The inner rotor is mounted for rotational and orbital movement relative the outer rotor and is supported and guided by the lobes of the outer rotor. The interacting external and internal lobes of the inner rotor and the outer rotor define a plurality of volume pressure chambers which expand and contract during the movement of the inner rotor. These known LSHT gerotors are restricted to a slow rotation speed of the drive shaft, since the shaft only rotates one cog per orbit of the inner rotor. These known LSHT gerotors comprises separate valve constructions for directing fluids. A further weakness of these types of gerotors is that they comprise oscillating parts resulting in vibrations and noise. These solutions are restricted to comprising several parts which provide a heavy and bulky solution. Further, these known solutions are restricted to solutions with a high cost comprising of several expensive and complex parts.
For the HSLT gerotors, the outer rotor rotates simultaneously with the inner rotor. The inner rotor rotates around a fixed axis and the outer ring slides within a housing. These known HSLT gerotors needs a wide gap between the housing and the lobes of the inner rotor and the outer ring. Thus, these known solutions result in a high leakage and low efficiency. These existing solutions provide constant efficiency losses and fluid leakage at high pressure.
The above mentioned problems can enhance each other as a combination of gerotors is used in a hydraulic transmission.
There is thus a need for an improved gerotor pump and motor, which reduces or preferably removing the above mentioned disadvantages.